Vibration dampers have been utilized for many years in torsional couplings, such as in the clutch driven member for an automotive vehicle power train to control engine induced torsional vibration in the connected elements of the power train. The vibration damper assembly is interposed in the clutch driven member ahead of a manually operated transmission to neutralize the torsional vibrations emanating from the vehicle engine, which vibrations would otherwise cause disturbing impact loads, pulsations and noises in the transmission and driveline. A vibration damper may also be utilized for a lock-up clutch inserted into a torque converter for an automatic transmission where the vibrations in the direct drive mode as a result of the lock-up between the torque input and the drive shaft would not be hydraulically dampened by the torque converter vibration damping characteristics.
A conventional vibration damper assembly consists of a clutch hub splined to the output shaft leading to the vehicle transmission and having an integral radial flange, a clutch plate and a spring retainer plate sandwiching the hub flange, and a plurality of compression springs received in circumferentially spaced axially aligned sets of openings in the plates and hub flange. The clutch plate and spring retainer plate are rigidly secured together and have limited rotation relative to the hub and flange, and annular friction pads are carried on the opposite surfaces of the clutch plate radially outwardly of the hub flange.
However, special circumstances may occur which will dictate a vibration damper having unusual characteristics so as to control objectionable vibration and/or gear rattle in a transmission which may occur during idling or under full engine load. Obviously, a conventional vibration damper will not be able to handle such special circumstances, but the present invention has such capabilities to overcome these problems.